Breastfeeding and Breast Milk: Research Activities and Scientific Advances

Institute Activities and Advances

Several NICHD organizational units (OUs) support and conduct research on breastfeeding and breast milk. Many of these efforts overlap and require trans-NICHD and trans-NIH collaboration. The following is only a summary of some of these efforts.

Pediatric Growth and Nutrition Branch (PGNB) research on breastfeeding is part of a larger research program on nutrition that uses a systems approach to incorporate biological, environmental, and other critical components as integral to public health. This program also explores nutritional variables, including those specific to breastfeeding, in both domestic and international contexts. Some of the PGNB projects related to breastfeeding include:

Elucidating the nutritional and bioactive components of breast milk, such as iron, and how these influence the duration of exclusive breastfeeding and the timing of introduction of supplemental or complementary foods;

Understanding the role of breast milk and its components in gastrointestinal immunity, prevention of respiratory disease, and prevention and treatment of infections and inflammation;

Identifying biomarkers for exposure, status, and function of vitamin D, zinc, and other nutrients and micronutrients and defining the long-term impacts of nutritional deficiency during infancy;

Exploring the nutritional needs of women with HIV/AIDS and how best to safely wean their infants to minimize exposure to the disease while still providing optimal nutrition, especially in resource-poor areas; and

Contributing scientific expertise to the World Health Organization (WHO), the United Nations World Food Programme, the President's Emergency Plan for AIDS Relief (PEPFAR), the NIH Office of AIDS Research, and other groups' guidelines and best practice recommendations on infant feeding and nutrition.

PGNB Study Results: Human Milk Protein Affects Infant Weight Gain

An increasing number of children worldwide are overweight or obese. Overweight and obese children are at a higher risk for a range of medical problems, including type 2 diabetes. Previous studies have indicated that children who were breastfed were less likely to become obese in early life, compared with children who were fed with infant formula. Scientists questioned whether adinopectin, a protein found in breast milk, could account for the lower weight in children who were breastfed. To better understand the relationship between breastfeeding and childhood obesity, researchers examined weight gain for the first 2 years of life in 192 infants. Scientists found that high levels of adinopectin in breast milk were associated with lower infant weight during the first 6 months of life, but also with accelerated weight gain in the second year of life. Combined, these results indicate that human milk adinopectin may help reduce weight gain early, but the infants may “catch up” and gain weight faster after breastfeeding has ended. Understanding these complex interactions may help reduce the risk of childhood obesity in the future. (PMID: 19500050)

The Institute's Pregnancy and Perinatology Branch (PPB) supports basic and clinical studies aimed at understanding the etiology, pathophysiology, therapy, and follow-up of health during the perinatal and neonatal periods, as well as research on in utero conditions and their influence on health outcomes. Among the PPB's projects within this context related to breastfeeding are:

Studies on the optimal timing of breastfeeding initiation, especially in resource-poor countries, and the effects on infant health outcomes, including infant mortality;

Research on the effects of breastfeeding on brain development, specifically development of the medullary raphe of the brainstem and the serotonin systems, and its mechanisms for reducing the risk for Sudden Infant Death Syndrome;

Investigations of how breast milk improves neurodevelopmental and other outcomes for neonates, including extremely LBW (ELBW) infants and preterm infants; and

Research on breast milk and its effects on severity of and treatment for certain newborn diseases, such as necrotizing enterocolitis, retinopathy of prematurity, and jaundice.

Many women experience depression during pregnancy and in the early months after childbirth. Previous studies showed a link between docosahexanoic acid (DHA) and positive mental health. DHA is also known to be important for optimal brain development in the growing fetus and in infants. Based on these earlier findings, researchers conducted a study to examine whether symptoms of depression during pregnancy affect the concentration of DHA in breast milk. Researchers conducted a survey of 287 women to assess whether they experienced depressive symptoms. Breast milk samples were collected from the same women 4 months after childbirth to measure the concentration of DHA. The results from the study showed that women who reported depressive symptoms in the first 20 weeks of pregnancy had lower concentrations of DHA in their breast milk. The same association was not found in women who reported depressive symptoms later in pregnancy. Because depression prior to pregnancy was not measured, it was unclear whether the women in this study were experiencing chronic depression or temporary depression due to stress or hormonal changes associated with pregnancy. However, because levels of DHA measured in breast milk are reflective of long-term influences on the body to store DHA over time, low levels of DHA in breast milk are likely associated with chronic depression. (PMID: 22223516)

PPB Study Results: What Predicts Intent to Breastfeed Exclusively?

All major medical organizations endorse exclusive breastfeeding for the first 6 months of life. However, only 13.3% of infants in the United States are exclusively breastfed through 6 months, with major differences in rates by maternal race, ethnicity, education, and income. Women who, while pregnant, form an intention to breastfeed their baby are most likely to do so. Scientists measured the association between intentions to exclusively breastfeed and knowledge of infant health benefits, feeding guidelines, and comfort related to breastfeeding in social settings. The study was conducted with a group of lower-income, ethnically diverse urban women. The results showed that 46% of women in the study intended exclusive breastfeeding, an equal proportion (46%) intended to use mixed feeding, and 8% intended to use formula feeding exclusively. Maternal knowledge about infant health benefits, as well as comfort with breastfeeding in social settings, was directly related to intention to exclusively breastfeed, and to breastfeed exclusively for longer periods of time. (PMID: 21342016)

The Maternal and Pediatric Infectious Disease Branch conducts and supports research on breast milk and breastfeeding within the context of HIV/AIDS infection and transmission. This research includes not only studies of the prevention of mother-to-child transmission (MTCT) of HIV/AIDS through a combination of limited duration of breastfeeding and medication interventions, but also the biological mechanisms by which MTCT occurs via breast milk. Additional studies examine the conditions that enhance or reduce the chance of transmission through breast milk, such as viral load and the number of mammary cells infected with HIV. Branch studies also aim to provide evidence about the best practices for breastfeeding, formula feeding, weaning, and supplementation for populations affected by HIV/AIDS. This research is conducted both domestically and abroad and includes partnerships and collaborations with other NIH Institutes and Offices, the WHO, PEPFAR, and other agencies and organizations in the United States and elsewhere.

The NICHD Population Dynamics Branch supports research on breastfeeding within the context of its social and societal impacts. Some of these studies aim to understand the home and socioeconomic factors that influence breastfeeding decisions, while other efforts aim to quantify the effects of workplace and public policies on breastfeeding and breastfeeding duration. This work also examines the range of breastfeeding impacts on communities and societies, from its influence on community connectedness to current and future economic health.

Researchers in the NICHD Division of Intramural Population Health Research also conduct research on breastfeeding and breast milk. These studies include (but are not limited to) the effects of maternal nutrition and malnutrition on breast milk composition and subsequent effects on fetal and infant nutrition. Additional research examines the factors that influence breastfeeding decisions, particularly among those in at-risk groups, including African American mothers who live in low-income areas, as well as the long-term effects of breastfeeding on chronic diseases, such as obesity.

Other Activities and Advances

As explained above, NICHD OUs collaborate with each other, with NIH Institutes and Centers, and with other governmental and non-governmental organizations in the United States and worldwide. Some of these partnership and activities are described below.

The NICHD PPB collaborated with the Centers for Disease Control and Prevention and the U.S. Food and Drug Administration to conduct the Infant Feeding Practices II Survey aimed at examining infant feeding practices, including breastfeeding, among a large cohort of women and the impacts of these practices on infant health.

The Neonatal Research Network (NRN), supported through the PPB, investigates the safety and efficacy of treatment and management strategies for newborn infants. The NRN has led several of the PPB's efforts on breastfeeding and neurodevelopmental outcomes for ELBW infants and on nutritional management of preterm, LBW, and ELBW infants.

The Biomarkers of Nutrition for Development project, led by the PGNB, aims to develop a unified approach to examine the scientific basis for choosing appropriate biomarkers for assessing the function and effect of diet and nutrition on health and disease in individuals and populations and for supporting the development and evaluation of evidence-based programs and policies to improve diet and nutrition as a way to improve health. Although the project does not focus specifically on breastfeeding or breast milk, these factors play a critical role in improving nutrition, especially in resource-poor areas of the world.